It is desirable to provide an operator with the capability of washing various fabrics and/or various sizes of loads of clothing in the same washing machine. To this end, automatic washing machines have long provided control features which allow the operator to vary the amount of water placed in the tub of the washing machine to match the size of the load of clothing to be laundered. If a small load is to be washed, then only a low level of water is needed. If a large load is to be washed, then a full level of water is required. The level of the water in the tub of the washing machine may also be varied for successive cycles in a laundering sequence, depending on whether a large or small load is being washed, and dependent upon other factors such as the degree of soiling to be removed, and whether the clothing is of a sturdy or delicate construction.
Water levels during various cycles of a given laundering process may also be varied to save energy by cutting down on the amount of heated water which is utilized, to thereby achieve higher energy efficiency ratings for the washing machine. In order to provide more functionality for the operator, and to improve energy efficiency, it has been necessary, through the years, that the water level control devices and systems used in automatic washing machines become more sophisticated. In order to provide the additional sophistication, without imposing undesirable additional costs and burden on the operator, it is desirable that a single, simple, adjustment of an operating mode selector by the operator be capable of simultaneously providing adjustment of multiple water level set points in the water level control mechanism.
Although the control of multiple water level settings can be accomplished relatively easily through the use of electronic control systems, such systems tend to be expensive in comparison to approaches where the water level settings of a liquid-level control switch are manually adjustable with a rotatable control knob. Unfortunately, heretofore, it has been necessary to provide several liquid level control switches, each having a separate control knob, in order to match the functionality provided by electronic systems. Having multiple manually operated liquid level control switches is undesirable in that operation of the washing machine becomes more complex for the operator, and results in undesirable increases in cost and reductions in reliability of the washing machine.
It is desirable, therefore, that an improved method and apparatus be provided for controlling liquid level in a washing machine through use of a minimum number of liquid level control switches having rotatable control knobs.
It is further desirable, in order to reduce inventory requirements and costs for the manufacturers of washing machines, that an improved method and apparatus be provided for constructing and operating a manually adjustable liquid-level control switch. In particular, it is desired that such an improved method and apparatus allow for external adjustment of water levels to be set simultaneously in accordance with a single manual input, so that washing machine manufacturers can readily make adjustments required to set the water levels to values desired for individual brands or models of machines.